X-rays on Magnetism and Domain Wall X rays on Magnetism and Domain Wall Motion

김 동 현김 동 현충북대학교 물리학과

2008.07.23

Soft X-ray Microscope at BL6.1.2, ALS

time resolutionelement specificity

Δt<70ps

lateral resolution

XMCD Contrast Mechanism for XM-1

absorberX-ray magnetic circular dichroism

right circ.

I0 I1 μ+

xg

I0 I1 μ−

(I /I ) =exp(- x)1 0 μ

element-specifichuge magnetic contrastM·σPhoton

spin-orbit information

1μm

Layer-Resolved Magnetic Imaging Using Element-Specificity

[Pt 0.75nm/Co 0.35nm]*50/Pt 3nm/Tb45Fe55 25nm

p yPhys. Rev. B, accepted (2008)

Fe L3 edge (706eV) Co L3 edge (777eV)

Magnetic Imaging at 15-nm Resolution with Element-Specificity

(C C ) Pt (50 )

p yJ. Appl. Phys (invited) 99, 08H303 (2006)

(Co84Cr16)87Pt13 (50nm)

10%)

TEM analysis

1

10

den

sity

(

0 10 20 30 40 50 600,1

num

ber

d

1,00

1,02

(a.u

.)

0 10 20 30 40 50 60n

grain size (nm)

►imaging at 0 96

0,98

inte

nsi

ty

Co L3 edge @777eV

►imaging at fundamental magnetic length scales

0 20 40 60 80 100 1200,96

distance (nm)

Co L3 edge @777eV

Imaging DW in Magnetic Ring Structures

Phys. Rev. Lett. (2007), Selected for Phys. Rev. Focus

PY ring and AMR measurementPY ring and AMR measurement

Direct Observation of Spin-Torque Phenomenon

1000-nm wide PY ring : Each step after spin-current pulses

Phys. Rev. Lett. 98, 187202 (2007), Selected for Phys. Rev. Focus

1000-nm wide PY ring : Each step after spin-current pulses

Before pulse After ten pulsesAfter ten pulses

Barkhausen Avalanche in Spin-Torque Phenomenon ?

Phys. Rev. Lett. 98, 187202 (2007), Selected for Phys. Rev. Focus

► Efficiency of DW displacement for 49 pulses of 1.0 ns width

Scaling Behavior of First Arrival Time of Traveling Domain Wallg

Phys. Rev. Lett. 100, 167204 (2008),

► Barkhausen avalanche phenomenon in CoCr and CoCrPt films and a scaling behavior of DW traveling time

Various Spin Fluctuation Phenomena

10000

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1000000

x 200

x 1000

x 500

tCo = 25 nm τ=4/3

) (A

. U.)

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1000

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100 1000 10000 10000010

100

1000

00 x 50P(

s)

2

Phys. Rev. Lett. (2003)

Jump Size, s (μm2)

Ph R L (2007) Phys Rev Lett (2008)Phys. Rev. Lett. (2007) Phys. Rev. Lett. (2008)

Spin Dynamics on ps-Timescale: Field-Driven Case

D.-H. Kim, in preparation

Element-Specific Imaging in Exchange-Biased System

edge -0.040A -0.050A -0.055A -0.060A -0.065A

Py(20nm)/FeMn(5nm)/CoFe(20nm)/Ta(5nm)

y

Ni

Co

Superp

osed

Element-Specific Imaging in Exchange-Biased System

edge -0.040A -0.050A -0.070A -0.080A -0.090A

Py(20nm)/FeMn(10nm)/CoFe(20nm)/Ta(5nm)

y

Ni

Co

Superp

osed